There are in principle various use cases of brakes for vibration absorbers. This applies both to vibration absorbers in wind turbines, but also to vibration absorbers in other slim structures, such as towers, masts, high-rise buildings.
In a first use case, the vibration absorber is always free. The absorber, for example of a wind turbine, is always in operation and must be captured and held by the damper for maintenance purposes.
In a second use case, the absorber is fixed during operation of the installation. The absorber, for example of a wind turbine, is switched off during operation of the installation and is intended to be switched on when the installation is put into operation or also in the case of a power outage. In this case, the absorber is used exclusively in order to safeguard the installations against Karmann vortex excitation. To this end, the absorber is operated only when the installation is at standstill. It must be absolutely guaranteed here that the absorber is reliably switched on in the case of standstill of the installation and/or in the case of a power outage.
In the third use case, the freely swinging absorber swings without braking during operation of the installation. In the case of particularly strong impacts, caused, for example, by gusts of wind, the tower of a wind turbine together with the vibration absorber is subjected to strong accelerations. Due to these accelerations, the absorber hits the end stop. In order to reduce or even prevent the impact if the absorber hits the stop, the absorber is “braked” with the aid of a brake.
In another use case, it is desirable to keep the damping of the absorber as low as possible, for example in the case of the rolling pendulum absorbers described here, which have a rotating pendulum mass alongside a main mass and are moved on a curved track. The side peaks arising in the case of these undamped systems are particularly high and can therefore have interfering effects. It therefore makes sense to brake the absorber in the frequency range less or greater (+/−10%) than the inherent frequency of the tower.
The object arising is thus to provide a brake device for pendulum absorbers, in particular rolling pendulum absorbers, for the use cases described and others, which can service the various braking and damping events, where appropriate in a targeted manner and controlled by corresponding current management.
The object has been achieved by the vibration absorbers described below and in the claims.